Noise Power Calculator

Calculator Inputs

Calculation Mode

Choose how the input noise floor is built.

Bandwidth Value

Integration bandwidth for total noise power.

Bandwidth Unit

Pick the scale for the bandwidth entry.

Temperature

Used for thermal noise density.

Temperature Scale

Kelvin is standard for RF thermal noise work.

Noise Figure (dB)

Applied only in thermal plus noise figure mode.

Gain (dB)

Adds output noise after input-referred calculations.

Implementation Loss (dB)

Optional margin for connectors, mismatch, or design loss.

Custom Density (dBm/Hz)

Used only in custom density mode.

Load Resistance (Ω)

Used for RMS voltage and current estimates.

Graph Points

Controls sweep resolution in the Plotly graph.

Example Data Table

These sample values are illustrative. They help verify your understanding before using project-specific inputs.

Mode	Bandwidth	Temperature	Noise Figure	Gain	Approx. Output Noise
Thermal + NF	1 MHz	290 K	3 dB	20 dB	≈ -91 dBm
Thermal Only	10 kHz	300 K	0 dB	0 dB	≈ -134 dBm
Custom Density	200 kHz	290 K	Ignored	15 dB	Depends on chosen density

Formula Used

Thermal noise power:
P_n = k × T × B

Thermal noise in dBm:
P_n,dBm = 10 × log₁₀(P_n / 1 mW)

Noise density from temperature:
N₀ = k × T and N_0,dBm/Hz = 10 × log₁₀(N₀ / 1 mW)

System input density with noise figure:
N_sys,dBm/Hz = N_{thermal,dBm/Hz} + NF + Loss

Total output noise power:
P_out,dBm = N_{effective,dBm/Hz} + 10 × log₁₀(B) + Gain

Noise factor and equivalent noise temperature:
F = 10^NF/10 and T_e = T₀(F − 1)

Here, k is Boltzmann’s constant, T is absolute temperature in kelvin, B is bandwidth in hertz, and T₀ is the standard reference temperature of 290 K.

How to Use This Calculator

Select the calculation mode that best matches your design case.
Enter the bandwidth and choose its unit.
Enter source temperature and select K, C, or F.
Add noise figure when modeling a real receiver chain.
Enter gain to estimate output noise after amplification.
Use implementation loss for practical design margin.
Use custom density mode when a measured floor is known.
Press the button to display results, exports, and the graph.

Frequently Asked Questions

1) What does this calculator estimate?

It estimates thermal noise density, integrated noise power, effective system noise, equivalent temperature, and output-referred noise after gain.

2) Why is temperature entered in kelvin?

Thermal noise equations require absolute temperature. Kelvin prevents negative absolute values and keeps the physics correct.

3) What is the role of bandwidth?

Noise accumulates across bandwidth. A wider bandwidth collects more noise power, so total noise rises with 10 log10 of bandwidth.

4) When should I use noise figure mode?

Use it when the receiver or amplifier adds internal noise beyond the source thermal floor. It is common in RF, microwave, and instrumentation work.

5) What is custom density mode for?

Use custom density mode when you already know a measured or specified noise floor in dBm per hertz and want total noise over bandwidth.

6) Why are voltage and current also shown?

Some engineers need noise in RMS electrical form. The calculator converts output power into RMS voltage and current using the entered load resistance.

7) Why is implementation loss included?

It gives a practical margin for losses, mismatch, or design penalties. This keeps estimates more realistic for hardware planning.

8) Does the graph show output noise or input noise?

The graph compares thermal input noise against system output noise across a bandwidth sweep. That makes gain and density effects easier to visualize.